Defect introduced paramagnetism and weak localization in two-dimensional metal VSe2

We have carried out a detailed investigation of the magnetism, valence state, and magnetotransport in VSe2 bulk single crystals, as well as in laminates obtained by mechanical exfoliation. In sharp contrast to the ferromagnetic behavior reported previously, here, no ferromagnetism could be detected for VSe2 single crystal and laminate from room temperature down to 2 K. Neither did we find the Curie paramagnetism expected due to the 3d 1 odd-electronic configuration of covalent V4+ ions. Rather, intrinsic VSe2 is a non-magnetic alloy without local moment. Only a weak paramagnetic contribution introduced by defects is noticeable below 50 K. A weak localization effect due to defects was also observed in VSe2 single crystals for the first time

The Associated Ion between the VDR Gene Polymorphisms and Susceptibility to Hepatocellular Carcinoma and the Clinicopathological Features in Subjects Infected with HBV

Aim. To evaluate the possible association between the vitamin D receptor (VDR), single-nucleotide polymorphisms (SNPs), and hepatocellular carcinoma (HCC) in patients with chronic hepatitis B virus (HBV) infection. Method. 968 chronic HBV infection patients were enrolled, of which 436 patients were diagnosed HCC patients, and 532 were non-HCC patients. The clinicopathological characteristics of HCC were evaluated. The genotypes of VDR gene at FokI, BsmI, ApaI, and TaqI were determined. Results. The genotype frequencies of VDR FokI C>T polymorphism were significantly different between HCC and non-HCC groups. HCC patients had a higher prevalence of FokI TT genotype than non-HCC subjects. With FokI CC as reference, the TT carriage had a significantly higher risk for development of HCC after adjustments with age, sex, HBV infection time, α-fetoprotein, smoking status, and alcohol intake. In addition, we also found that the TT genotype carriage of FokI polymorphisms were associated with advanced tumor stage, presence of cirrhosis, and lymph node metastasis. The SNP at BsmI, ApaI, and TaqI did not show positive association with the risk and clinicopathological features of HCC. Conclusion. The FokI C>T polymorphisms may be used as a molecular marker to predict the risk and to evaluate the disease severity of HCC in those infected with HBV

Reconstructing 1D Fe Single‐atom Catalytic Structure on 2D Graphene film for High‐efficiency Oxygen Reduction Reaction

The ordinary intrinsic activity and disordered distribution of metal sites in zero/one-dimensional (0D/1D) single-atom catalysts (SACs) lead to inferior catalytic efficiency and short-term endurance in the oxygen reduction reaction (ORR), which restricts the large-scale application of hydrogen−oxygen fuel cells and metal−air batteries. To improve the activity of SACs, a mild synthesis method was chosen to conjugate 1D Fe SACs with 2D graphene film (Fe SAC@G) that realized a composite structure with well-ordered atomic-Fe coordination configuration. The product exhibits outstanding ORR electrocatalytic efficiency and stability in 0.1 M KOH aqueous solution. DFT-D computational results manifest the intrinsic ORR activity of Fe SAC@G originated from the newly-formed FeN4−O−FeN4 bridge structure with moderate adsorption ability towards ORR intermediates. These findings provide new ways for designing SACs with high activity and long-term stability

Probing Ligand-Induced Cooperative Orbital Redistribution That Dominates Nanoscale Molecule–Surface Interactions with One-Unit-Thin TiO 2 Nanosheets

Understanding the general electronic principles underlying molecule–surface interactions at the nanoscale is crucial for revealing the processes based on chemisorption, like catalysis, surface ligation, surface fluorescence, etc. However, the electronic mechanisms of how surface states affect and even dominate the properties of nanomaterials have long remained unclear. Here, using one-unit-thin TiO2 nanosheet as a model surface platform, we find that surface ligands can competitively polarize and confine the valence 3d orbitals of surface Ti atoms from delocalized energy band states to localized chemisorption bonds, through probing the surface chemical interaction at the orbital level with near-edge X-ray absorption fine structure (NEXAFS). Such ligand-induced orbital redistributions, which are revealed by combining experimental discoveries, quantum calculations, and theoretical analysis, are cooperative with ligand coverages and can enhance the strength of chemisorption and ligation-induced surface effects on nanomaterials. The model and concept of nanoscale cooperative chemisorption reveal the general physical principle that drives the coverage-dependent ligand-induced surface effects on regulating the electronic structures, surface activity, optical properties, and chemisorption strength of nanomaterials

Unusual Enrichment and Assembly of TiO₂ Nanocrystals at Water/Hydrophobic Interfaces in a Pure Inorganic Phase

We report an unusual enrichment and assembly of TiO₂ nanocrystals at water/hydrophobic interfaces through oxidative hydrolysis of TiCl₃ in water. The assembly is a spontaneous process that involves on-water inorganic reaction and assembly in the absence of any organic phases. In this process, TiO₂ nanoparticles are preferentially produced at water/hydrophobic interfaces. When the surface tension of the aqueous phase is above a critical value, ca. 25–35 mN m^–1, these TiO₂ nanocrystals can spontaneously accumulate at water/air interfaces to produce macroscopic sized sheets and tubes

Fe–N–C single-atom catalysts with an axial structure prepared by a new design and synthesis method for ORR

Fe–N–C single-atom catalysts usually exhibit poor ORR activity due to their unsatisfactory O2 adsorption and activation. Here, a new design idea and tailored self-assembly synthesis method are reported to improve their ORR performance. DFT calculations indicate that the ORR electrocatalytic activity of Fe–N–C single-atom catalysts with an axial structure is superior to that of Fe–N–C single-atom catalysts with a Fe–N4 active site. In order to experimentally demonstrate the difference, Fe–N–C single-atom catalysts with a Fe–N5 active site were successfully synthesized on the surface of monolayer graphene. XANES, SEM, HRTEM, XRD, Raman and XPS analyses indicate that the synthesized Fe–N–C catalyst possessed nanofibre morphology and a curved layer-like crystal structure. For comparison, FePc powder was used as the FePc(Fe–N4) catalyst as its molecular structure involves a Fe–N4 active site embedded in carbon six-membered rings. The current density of the synthesized Fe–N5/C@G catalyst at a potential of 0.88 V vs. RHE is 1.65 mA cm−2, which is much higher than that of the FePc(Fe–N4) catalyst (1.04 mA cm−2) and even higher than that of commercial Pt/C catalyst (1.54 mA cm−2). The results are very well consistent with the DFT calculations, verifying the dependability and accuracy of DFT calculations. This work reports a new synthetic idea to obtain better performance and proposes a formation mechanism to explain the process of the synthesis method